Experimental And Engineering Model Investigation Of Condensation In Micro-fin Tubes Of Different Geometries

Two-phase flow and compact heat exchanger, which are hotspots in heat and mass transfer in recent years, are widely used in engineering. But the complicated flow process and large amount of impact factors lead to difficulty to derive the analytic solution of two-phase flow. The experimental data is hard to predicted within a relatively low error band level using the existing correlations for two-phase flow. So it is hoped that a generalization of data getting from the experiments will help to optimize the existing correlations.Three parts of work are done in this paper. At first a literature review of two-phase flow in tubes was completed. Secondly, an experimental facility for in-tube condensation was designed and built. Finally the experimental data analysis and the optimization of some correlations were carried out.An experimental investigation was performed with R22for single-phase flow and condensation inside four micro-fin tubes with the same outer diameter5mm and helix angle18°. Data are for mass fluxes ranging from about200to650kg/m2s. The nominal saturation temperature is320K, with inlet and outlet qualities of0.8and0.1, respectively. The results suggest that tube4has the highest heat transfer coefficient and the highest pressure drop. Tube1almost has the same heat transfer coefficient as Tube4, however, with a lower pressure drop penalty than Tube4when G≥400kg/(m2s). In addition, Pressure drop correlations for plain tubes were applied to micro-fin tubes by using a friction factor calculated by the Churchill model and a suitable relative roughness. The Kedzierski and Goncalves correlation has been modified to be based on the nominal heat transfer area adopting the fin root diameter instead of the actual inner surface heat transfer area, which can predict all data points within a±20%error band.